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interpolate

This method is used to interpolate the given string with the given values or with environment variables / system properties. 
import static io.github.boykaframework.utils.StringUtils.interpolate;
. . .
System.out.println (interpolate ("${env:USER_NAME}"));

. . . OR . . .

Map<String, String> values = new HashMap<> ();
values.put ("USER_NAME", "wasiq");

System.out.println (interpolate ("${USER_NAME}", values));
:::tip You can explore all the available formats for interpolation in Web configuration info section. :::